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571e768202
Before pushing pcounter to Linus tree, I would like to make some adjustments.
Goal is to reduce kernel text size, by unlining too big functions.
When a pcounter is bound to a statically defined per_cpu variable,
we define two small helpers functions. (No more folding function
using the fat for_each_possible_cpu(cpu) ... )
static DEFINE_PER_CPU(int, NAME##_pcounter_values);
static void NAME##_pcounter_add(struct pcounter *self, int val)
{
__get_cpu_var(NAME##_pcounter_values) += val;
}
static int NAME##_pcounter_getval(const struct pcounter *self, int cpu)
{
return per_cpu(NAME##_pcounter_values, cpu);
}
Fast path is therefore unchanged, while folding/alloc/free is now unlined.
This saves 228 bytes on i386
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
74 lines
1.9 KiB
C
74 lines
1.9 KiB
C
#ifndef __LINUX_PCOUNTER_H
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#define __LINUX_PCOUNTER_H
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/*
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* Using a dynamic percpu 'int' variable has a cost :
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* 1) Extra dereference
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* Current per_cpu_ptr() implementation uses an array per 'percpu variable'.
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* 2) memory cost of NR_CPUS*(32+sizeof(void *)) instead of num_possible_cpus()*4
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*
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* This pcounter implementation is an abstraction to be able to use
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* either a static or a dynamic per cpu variable.
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* One dynamic per cpu variable gets a fast & cheap implementation, we can
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* change pcounter implementation too.
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*/
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struct pcounter {
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#ifdef CONFIG_SMP
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void (*add)(struct pcounter *self, int inc);
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int (*getval)(const struct pcounter *self, int cpu);
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int *per_cpu_values;
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#else
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int val;
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#endif
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};
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#ifdef CONFIG_SMP
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#include <linux/percpu.h>
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#define DEFINE_PCOUNTER(NAME) \
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static DEFINE_PER_CPU(int, NAME##_pcounter_values); \
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static void NAME##_pcounter_add(struct pcounter *self, int val) \
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{ \
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__get_cpu_var(NAME##_pcounter_values) += val; \
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} \
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static int NAME##_pcounter_getval(const struct pcounter *self, int cpu) \
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{ \
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return per_cpu(NAME##_pcounter_values, cpu); \
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} \
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#define PCOUNTER_MEMBER_INITIALIZER(NAME, MEMBER) \
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MEMBER = { \
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.add = NAME##_pcounter_add, \
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.getval = NAME##_pcounter_getval, \
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}
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static inline void pcounter_add(struct pcounter *self, int inc)
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{
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self->add(self, inc);
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}
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extern int pcounter_getval(const struct pcounter *self);
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extern int pcounter_alloc(struct pcounter *self);
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extern void pcounter_free(struct pcounter *self);
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#else /* CONFIG_SMP */
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static inline void pcounter_add(struct pcounter *self, int inc)
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{
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self->val += inc;
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}
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static inline int pcounter_getval(const struct pcounter *self)
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{
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return self->val;
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}
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#define DEFINE_PCOUNTER(NAME)
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#define PCOUNTER_MEMBER_INITIALIZER(NAME, MEMBER)
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#define pcounter_alloc(self) 0
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#define pcounter_free(self)
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#endif /* CONFIG_SMP */
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#endif /* __LINUX_PCOUNTER_H */
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